Changeover controller for seriesparallel hydraulic pump



Nov. 12, 1963 N. H. SMITH 3,110,254

CHANGEOVER CONTROLLER FOR SERIES-PARALLEL HYDRAULIC PUMP Filed July 5, 1962 INVE OR.

United States Patent 3,110,264 CHANGEGVER (IONTRGLLER FGR SERIES- PARALLEL HYDRAULIC PUMP Norman H. Smith, Elmira, N.Y., assignor to Steriing Precision Corporation, Elmira, N.Y., a corporation of Delaware Filed July 3, 1962, Ser. No. 207,348 4 Claims. (Cl. 103106) This invention relates to a changeover controller for a series-parallel hydraulic pump and more particularly to such a controller which is operated completely by pressure from the pump for shifting it from series to parallel operation and vice versa.

Series-parallel hydraulic pumps with controls for shifting the operation from one to the other have long been in common use, particularly in fire fighting equipment, the pumps being selectively placed in parallel when high volume low pressure water is required or in series when high pressure low volume water is required.

The principal object of the present invention is to provide such a series-parallel hydraulic pump in which the manual control for shifting from one operation to the other is self-energized, the changeover being motivated by a difierential area piston valve in conjunction with the difierential in water pressure between the suction and outlet sides of the pumps.

Another object is to provide such a changeover control which is simple and reliable in construction and operation.

Other objects and advantages will be apparent from the following description and drawings in which:

FIG. 1 is a diagrammatic section through a seriesparallel pump having a changeover controller embodying the present invention and showing the parts positioned for operation in parallel, that is, to supply a large volume of low pressure water.

:FIG. 2 is a view similar to FIG. 1 but showing the parts positioned for series operation to supply a smaller volume of water at high pressure.

It has long been common practice in fire fighting equipment to have two centrifugal pumps 1 and 2 having impellers 3 and 4' mounted on a common shaft 5 journalled in the pump housing 6 and driven by an electric motor 3. In the series-parallel pump illustrated, the first stage pump is designated at 1 and the second stage pump at 2. The impeller 4 is shown as supplied with water from passages 9 and the impeller 3 is shown as supplied with water from passages 14 these passages being suitably formed in the pump casing 6 and having their inlet ends connecting with a branched supply Y 11 which can be assumed to be supplied with water from city hydrants for tire fighting purposes. The inlet of each of the passages 9 has a check valve 12, these check valves opening toward the centrifugal pump impellers 4.

The outlet from the second stage pump 2 discharges into a passage 13 which discharges into an outlet chamber 14 extending transversely of the pump casing 6 and having outlet lines 15 which lead to the equipment being served and through which a lange volume of low pressure water or a small volume of high pressure water is supplied to such equipment.

The outlet from the first stage pump 1 discharges into a passage 16 leading to a changeover chamber 18. A port 19 connects this changeover chamber 18 with the outlet chamber 14, this port being surrounded by a valve seat 24} opening toward the changeover chamber 18. A port 21 connects the changeover chamber 18 with a passage 22 the outlet end of which opens into one of the supply passages 9. The port 2 1 is provided with a valve ice seat 23 which is coaxial With and opposes the valve seat 24 I The head 25 of a changeover valve is arranged in the changeover chamber 18 and is provided with valve surfaces 26 and 28 arranged to seat respectively on the valve seats 2% and 23, the valve head being mounted for this purpose on a stem 29 which is coaxial with the ports 19 and 21. This stem extends through the port 19 and outlet chamber 1 and has a piston 30 contained within a cylinder 31. A helical compression spring 32 is interposed between the piston 30 and the cylinder head 33 and biases the piston 30 and valve head 25 into engagement with the seat 23 as illustrated in FIG. 1. An important feature of the changeover valve is that it is a difierential area piston valve, the area of the piston 3%} being greater than the effective area of the valve head 25.

A hydraulic control line 34 connects the cylinder 31 with a manual selector valve 35. This valve is constructed to connect the control line 34 either with a line 36 connecting with the outlet chamber 14 common to the two pumps 1 and 2, or with a line 38 connecting with one of the inlet conduits 9. By this arrangement it will be seen that the control valve 35 can connect the control line 34 either with pump pressure (via line 36) or with pump suction (via line 38).

When a large volume of low pressure water is desired the control valve 35 is turned to connect the lines 34 and 36. in this position outlet pressure from at least the pump 2, through the passage 13, chamber 14, opening 19 and chamber 18, is impressed on the valve head 25 and also on the left hand side of the piston 30 as viewed in the drawings. However, this same pressure is impressed on the right hand side of the piston 30. Because of the larger size of this piston 30 as compared with the valve head 25, this moves the piston and valve head 30, 25 to the left, causing valve head 25 to seat on the valve seat 23 thereby to close port 21 and open port 19.

Accordingly, the pumps 1 and 2 operate in parallel as illustrated in FIG. 1. Thus Water from the branched inlets 11 passes through the conduits 9 and 10 to the inlets of the rotors 4 and 3 which discharge through the passages 16 and 13 into the changeover chamber 18 and common outlet chamber 14, respectively. Since these chambers 18 and 14 are now in communication with each other via the now open port 19, the water from both pumps passes through this common outlet chamber 14 and out through the outlet lines 15. Since the pump rotors 3 and 4 are now operating in parallel, a large volume of Water is supplied at low pressure.

When high pressure water is required, the operator turns the selector valve 35 to connect the control line 34 with the line 38. Since this line 38 connects with one of the pump inlet passages 10 and since this passage is on the suction side of the pump 1, the pressure of the hydraulic liquid contained within the cylinder 31 is reduced in relation to the pressure in the chamber 14 which is at pump outlet pressure.

This pressure difierential on opposite sides of the piston at! moves the piston to the right thereby to unseat the piston head 25 from the seat 23 and to seat it against the seat 29 of the port 19. Accordingly, the pumps 1 and 2 are now shifted to series operation as illustrated in FIG. 2. Thus while the second stage pump 2 is still discharging via the passage 13 into the common outlet chamber 14 and thence to the lines 15 leading to the apparatus being served, the discharge of the first stage of the pump 1 through the passage 16 into changeover chamber 18 escapes through the now open port 21 into the passage 22 leading to one of the inlet passages 9 serving the second stage pump 2. Accordingly, the discharge from first stage pump -1 is conducted to the inlet of the second stage pump 2 so that these two pumps now act in series to provide a low volume high pressure output through the common outlet chamber 14 and lines 15 leading to the apparatus being served.

When the pumps 1 and 2 are so operating in series, the check valves 12 are closed and all of the Water is supplied through the passages leading to the inlet of the first stage pump 1.

From the foregoing, it will be seen that the present invention provides a very simple and effective changeover control for shifting a series-parallel pump from one service to the other, utilizing the differential between the inlet and outlet pressure of the pump for such changeover.

I claim:

1. In a series-parallel pumping apparatus having a first stage pump with an inlet and an outlet and a second stage pump with an inlet and an outlet; the combination therer with of a changeover control for shifting said pump from parallel to series operation and vice versa, comprising (A) means providing a common outlet for both of said (B) means providing a changeover chamber in communication with the outlet of said second stage pump,

(C) means providing a first port between said changeover chamber and said common outlet,

(D) means providing a second port between said changeover chamber and said inlet to said second stage pump,

(E) a valve head movable to open and close said ports alternately,

("F) piston means actuating said valve head, and

(G) a selector valve selectively placing said piston means '(a) in communication with the inlet of one of said pumps to move said valve head into closing engagement with said first port thereby to provide a series flow through said pumps With the flow from said first stage pump being via its outlet, said changeover chamber, second port to the inlet of said second stage pump and (b) in communication with the outlet of one of said pumps to move said valve head into closing engagement with said second port thereby to provide a parallel fiow through said pumps with the flow from said first stage pump being via its outlet, said changeover chamber and first port directly to said common outlet.

2. The combination set forth in claim 1 wherein a check valve is arranged in said inlet of said second stage pump and opens toward said second port thereby to close said inlet to said second stage pump in response to pressure from said first stage pump.

3. The combination set forth in claim 1 wherein said ports are in opposite side walls of said changeover chamber, and wherein said valve head comprises a single head in said changeover chamber movable to close one or the other of said ports.

4. The combination set forth in claim 1 wherein said piston means is a piston of large or efiective area than said valve head and contained in a cylinder and is connected to said valve head by a common stem.

References Cited in the file of this patent UNITED STATES PATENTS 2,957,426 Miller Oct. 25, 1960 FOREIGN PATENTS 554,326 France Feb. 28, 1923 73,159 Germany Jan. 25, 1894 

1. IN A SERIES-PARALLEL PUMPING APPARATUS HAVING A FIRST STAGE PUMP WITH AN INLET AND AN OUTLET AND A SECOND STAGE PUMP WITH AN INLET AND AN OUTLET; THE COMBINATION THEREWITH OF A CHANGEOVER CONTROL FOR SHIFTING SAID PUMP FROM PARALLEL TO SERIES OPERATION AND VICE VERSA, COMPRISING (A) MEANS PROVIDING A COMMON OUTLET FOR BOTH OF SAID PUMPS, (B) MEANS PROVIDING A CHANGEOVER CHAMBER IN COMMUNICATION WITH THE OUTLET OF SAID SECOND STAGE PUMP, (C) MEANS PROVIDING A FIRST PORT BETWEEN SAID CHANGEOVER CHAMBER AND SAID COMMON OUTLET, (D) MEANS PROVIDING A SECOND PORT BETWEEN SAID CHANGEOVER CHAMBER AND SAID INLET TO SAID SECOND STAGE PUMP, (E) A VALVE HEAD MOVABLE TO OPEN AND CLOSE SAID PORTS ALTERNATELY, (F) PISTON MEANS ACTUATING SAID VALVE HEAD, AND (G) A SELECTOR VALVE SELECTIVELY PLACING SAID PISTON MEANS (A) IN COMMUNICATION WITH THE INLET OF ONE OF SAID PUMPS TO MOVE SAID VALVE HEAD INTO CLOSING ENGAGEMENT WITH SAID FIRST PORT THEREBY TO PROVIDE A SERIES FLOW THROUGH SAID PUMPS WITH THE FLOW FROM SAID FIRST STAGE PUMP BEING VIA ITS OUTLET, SAID CHANGEOVER CHAMBER, SECOND PORT TO THE INLET OF SAID SECOND STAGE PUMP AND (B) IN COMMUNICATION WITH THE OUTLET OF ONE OF SAID PUMPS TO MOVE SAID VALVE HEAD INTO CLOSING ENGAGEMENT WITH SAID SECOND PORT THEREBY TO PROVIDE A PARALLEL FLOW THROUGH SAID PUMPS WITH THE FLOW FROM SAID FIRST STAGE PUMP BEING VIA ITS OUTLET, SAID CHANGEOVER CHAMBER AND FIRST PORT DIRECTLY TO SAID COMMON OUTLET. 